var qt = wx.createSelectorQuery();
    qt.select('#bbs').fields({ node: true, size: true }).exec((res) => {
      let canvas = res[0].node;
      canvas.width = self.page.data.windowWidth;
      canvas.height = self.page.data.windowHeight;
      let layer = canvas.getContext('2d');
      let img1 = canvas.createImage();
      img1.src = '/image/2.png';
      img1.onload = function (res) {
        console.log('onload成功')
        layer.drawImage(img1, 300, 10, 300, 300);
          //方法不执行
      }
      img1.onerror = function (res) {
        console.log('onload失败')
        //实际执行了此方法
      }


    })

微信iOS 7.0.20 版本 使用canvas 2d 绘制drawImage时无法成功绘制，图片不显示，img1.onload不执行，执行了img1.onerror函数，img对象无法onload成功，微信iOS 7.0.18是正常的。